1. Field of the Invention
The present invention relates to a transmitter of a mobile station in a CDMA (Code Division Multiple Access) communications system, and more particularly to such transmitter for controlling the channel gain of a transmitted binary signal and integer-spreading it.
2. Description of the Related Art
Referring to FIG. 1 for illustrating the structure of the transmitter of a mobile station in a conventional CDMA communications system, the orthogonal modulator 111 multiplies the transmitted signal of each channel by a corresponding orthogonal code of the channel to orthogonal spread the channel. The orthogonal code may be a Walsh code. The long PN (pseudo-noise) code spreader 113 and short PN code spreader 115 spread the transmitted signal of each channel modulated with the orthogonal code. The long code is for identifying the mobile station, and the short code is for identifying the base station. The base band filter 117 filters the spread transmitted signal into the base band. The modulator 119 modulates the transmitted signal of the base band with a carrier wave.
Such a conventional transmitter of the mobile station spreads binary data which has not been adjusted for channel gain after orthogonal modulation, and then filters the spread binary data, so that it requires a circuit for binary mapping to obtain binary data. Furthermore, additional multipliers are necessary for spreading the obtained binary data in long code and short code, complicating the hardware structure. Although FIG. 1 does not show the additional parts for gain adjustment, it will be readily noted that the circuit for binary mapping is required including additional multipliers.
It is an object of the present invention to provide a CDMA mobile phone with a simplified circuit for adjusting the channel gain, and method therefor.
It is another object of the present invention to provide a CDMA mobile phone with a simplified circuit for band spreading, and method therefor.
It is another object of the present invention to provide a CDMA mobile phone with a circuit for band spreading with adjustment of the channel gain without binary mapping.
According to the present invention, a transmitter provided in the mobile station of the CDMA communications system comprises an orthogonal modulator for orthogonal-modulating channel-coded transmission signals with the orthogonal codes of corresponding channels, a gain control value generator for obtaining the complement of a first channel gain control value corresponding to each channel to generate a second channel gain control value, and a selection circuit for selecting one of the first and second channel gain control values by the orthogonal-modulated signals.
The present invention will now be described more specifically with reference to the drawings attached only by of example.